"Forrest Gump" star Gary Sinise and his wife, Moira Harris, are grieving the loss of their son, McCanna ‘Mac’ Sinise, who passed away at the age of 33 in January. Mac Sinise succumbed to a rare form of cancer known as chordoma.

In a detailed obituary shared on his nonprofit's website, the "CSI: NY" star disclosed that his son had been working for him at the Gary Sinise Foundation when he received the cancer diagnosis.

Mac Sinise was diagnosed in 2018, around the same time his mother, Harris, faced a stage 3 breast cancer diagnosis. While Harris recovered, her son spent the subsequent years battling chordoma, a slow-growing bone cancer that typically originates at the top or bottom of the spine, as outlined by the Mayo Clinic.

In his online tribute, Gary Sinise expressed that his son had been an "inspiration" to their family throughout his battle with cancer.

"An incredible inspiration to those who knew and loved him, he faced his battle with grace, courage, and love," the obituary states. "Even with one setback after another, he never stopped living and learning, creating, and giving, and loving."

Mac Sinise passed away on January 5, 2024, and was laid to rest on January 23, according to the obituary.

In the final stages of his life, Mac Sinise turned to his lifelong passion for music. With assistance from friends and collaborators, he composed and recorded an album titled "Resurrection & Revival." Gary Sinise noted that his son's album serves as a parting gift to the family, destined to live "in our hearts forever."

"While our hearts ache at missing him, we are comforted in knowing that Mac is no longer struggling, and inspired and moved by how he managed it,” Gary Sinise expressed. “He fought an uphill battle against a cancer that has no cure, but he never quit trying.”

“I am so blessed, fortunate, and proud to be his dad,” he added.

Gary Sinise concluded the obituary by stating that he will miss his son "for eternity."

"We were blessed to have you in our lives as a son, brother, and friend...and we will miss you and love you for eternity."